PHASE-BEHAVIOR IN MIXTURES OF A HOMOPOLYMER AND A BLOCK-COPOLYMER .4.SALS AND SAXS STUDIES

Phase behavior of blends of poly(vinyl methyl ether) (PVME) with four styrene-butadienestyrene (SBS) triblock copolymers, being of various m olecular weights, architecture, and compositions, was investigated by small-angle light scattering. Small-angle X-ray scattering investigati on was accomplished for one blend. Low critical solution temperature ( LCST) and a unique phase behavior, resembling upper critical solution temperature (UCST), were observed. It was found that the architecture of the copolymer greatly influenced the phase behavior of the blends. Random phase approximation theory was used to calculate the spinodal p hase transition curves of the ABA/C and BAB/C systems; LCST and resemb ling UCST phase behavior were observed as the parameters of the system changed. Qualitatively, the experimental and the theoretical results are consistent with each other. (C) 1996 John Wiley & Sons, Inc.